EHV-1 Identified in Gallatin County, Mont., Horse

A 6-year-old mare in Gallatin County, Mont., has tested positive for equine herpesvirus-1 (EHV-1), the Montana Department of Livestock reported March 25. Officials say this case is not related to an EHV-1 case in Flathead County, Mont., reported late last week.

“We have another case of EHV-1, but let me stress that there is no connection to the earlier case,” said Assistant State Veterinarian Tahnee Szymanski, DVM. “Fortunately, the Gallatin County case, like the Flathead case, appears to be an isolated event.”

The affected mare arrived in Montana three weeks ago from southern California. The horse began showing clinical signs of disease last week; test results received Saturday (March 23) morning confirmed presence of the virus. The horse is housed at a boarding and training facility, which is currently under quarantine, in Gallatin County. An encouraging sign, Syzmanski said, is that none of the other horses at the facility have shown any clinical signs of contracting the virus.

“The manager and trainers at the facility has been great to work with, and are letting all of their clients know about the incident,” Szymanski said.

EHV-1 is naturally occurring in equine populations and can cause respiratory disease, abortion in mares, neonatal foal death, and/or neurologic disease. There are two types of the virus responsible for outbreaks in the United States: the neuropathogenic form and the wild type. The horse in Gallatin County, as well as the horse in Flathead County, appear to have been infected with the less virulent wild type.